Fertilizer comes in many chemical compounds, and some of them are water-soluble. Liquid fertilizer is nothing more than a solution of these compounds in water. Common examples of the various water-soluble compounds that might be used by a fertilizer manufacturer to provide nutrients are urea, ammonium phosphate and ammonium nitrate. Because these compounds are in liquid form they can reach the roots much faster, resulting in immediate benefits.
Liquid fertilizers can be bought commercially, or they can be produced at home by the do-it-yourself gardener. Either way, they provide a quick pick-me-up to plants around the home and garden.
As required by Federal law, the relative amounts of the different types of fertilizer are clearly marked on the container with a series of numbers. An example would be 20-15-5, which stands for 20 percent nitrogen, 15 percent phosphorus and 5 percent potassium. Easy to use, the commercial brands either are applied straight from the container or are required to be mixed first with additional water. Commercial liquid fertilizers can be either synthetic or organic based.
Allowing compost to soak in water for several days while providing it with a source of oxygen creates a liquid that has become known as "compost tea." Rich in microorganisms, this tea is filtered through cheesecloth to remove larger debris, diluted with about a 10 to 1 ratio of water and then either foliar sprayed directly onto plants or used to water the roots. The adequacy of compost tea as a fertilizer depends upon the quality of the initial compost and other ingredients. If high value nitrogen sources such as alfalfa, comfrey or fish emulsion are used in the tea, then the nitrogen ratio in the tea will be higher.
Animal Manure Tea
An alternative to compost tea is manure tea made from the manure of horses, cows, poultry, rabbits or other herbivores. Made the same way as compost tea, it has many of the same benefits. This tea is best used around non-vegetable plants to avoid any potential transfer of harmful bacteria to food products.
Used since prehistoric times, human urine is high in nitrogen, potassium, phosphate and other nutrients. Sterile from a healthy individual, urine can significantly increase production over not using any fertilizer. At 100 percent strength it can be too strong for most plants, and it is generally recommended using at a 4 to 1 water to urine ratio. A 2008 study reported in the Journal of Agricultural and Food Chemistry using 20 taste testers for tomatoes grown with human urine compared to traditional fertilizers reported that "all tomato samples were evaluated as being equally good by the tasters..." The report also showed that the tomato plants produced 4.2 times the tomatoes versus plants that were not fertilized.